Hi GS, thanks for your reply!
Yes, I've seen your comment.
In a nutshell we're a backup vendor and we are trying to support backing up FT VM's out of the box if possible.
We usually rely on the CreateSnapshot_Task API call, as described here:
and this enables us to leverage quiescing, CBT and so on.
Some pages (including this thread) quite emphatically state that this is now supported with vsphere 6.0 as long as it's called through the API.
A couple of examples:
http://www.running-system.com/vsphere-6-fault-tolerance-highlights-improvements/
http://www.vmwarearena.com/2015/02/vsphere-6-0-whats-new-in-vmware-fault-tolerance-ft.html
However, the usual CreateSnapshot_Task API call as described above does not seem to work with FT in practice, and in fact some sites (links in my previous post) mention "disk-only" or "storage" snapshots which are different to the usual ESXi snapshots, but I can't seem to find clear documentation about whether there is a different API to achieve this.
Thanks for any insight you may have on this